Influence of cation chemical composition and structure on the double layer capacitance for Bi(1 1 1)|room temperature ionic liquid interface

Cyclic voltammetry, electrochemical impedance spectroscopy, and computational chemistry methods have been applied for investigation of electrochemically polished Bi(1 1 1) electrode in 1-butyl-4-methylpyridinium tetrafluoroborate (BMPyBF4) ionic liquid. The region of ideal polarizability, series resistance and capacitance, limiting high-frequency and low-frequency capacitances have been obtained and compared with those established for 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4). Differently from Bi(111)|EMImBF4 interface, noticeably more expressed influence of the mass transfer limited step on the electrical double layer formation kinetics has been demonstrated and explained by the higher viscosity of BMPyBF4. Possible reasons of the lower values of series capacitance for Bi(111)|BMPyBF4 compared with Bi(1 1 1)|EMImBF4 interface has been examined on the basis of modern theoretical models.

► The Bi|ionic liquid interface has been studied and modelled.
► Electrical double layer structure depends on chemical composition of ionic liquid.
► Adsorption kinetics depends on viscosity of ionic liquid.
► Addition of acetonitrile to ionic liquid increases double layer capacitance.